Gas arc welding with automatically controlled, robotic systems has been increasingly investigated and used because of the improvements it offers in productivity and weld consistency. Such welding systems have been developed in which the control system detects the weld joint and weld conditions by the formation of an optical image of the area around the arc and the projection of that image onto a video sensor for electronic analysis. One of the most desirable welding systems utilizes a generally tubular torch having the electrode extending from its open lower end and having an internal lens for focusing an image of the weld scene upon the end of a fiber optics cable which extends into the opposite, upper end of the torch. Torches of this type are shown in U.S. Pat. Nos. 4,450,339; 4,488,032; and 4,491,719. Still other torches have TV cameras mounted directly to the torch.
It is desirable that the electrode be mounted in the torch in a manner which facilitates its easy replacement and adjustment with a minimum of manual manipulation since this is done often during production. Not only must the electrode be easily changeable and yet held rigidly during operation but, in addition, it is desirable that it be supported in a manner which can provide substantial heat flow to allow transfer of heat from the electrode out of the torch at a high rate while simultaneously not blocking the optical path between the arc region and the end of the fiber optic cable. It is also desirable that the electrode support system provide a light blocking or masking means around the axis of the electrode to prevent image distortion caused by the excessively intense light radiating from the arc itself.
The electrode in the three patents cited above is supported by a cantilevered strut extending to the axis of the torch. Although that electrode support does provide an adequately open and unblocked optical passageway from the arc region to the image detecting system, it has a heat flow path having a relatively small cross section and relatively small contact area with the electrode and therefore provides inadequate thermal conductivity.
One object and feature of the present invention is to provide an electrode mounting structure which greatly improves the total cross section of the heat transfer path in order to allow a higher heat conduction rate from the electrode to the torch body while at the same time not blocking the vision of the imaging system.
The electrode mounting structure of the above three patents also requires a separate collar for blocking the light in the immediate vicinity of the arc. It is an object of the present invention to eliminate the need for this separate collar and therefore its manipulation during electrode change or adjustment while maintaining blockage of the intense light from the immediate vicinity of the arc.
It is another object and purpose of the present invention to provide an electrode mounting structure which can accomplish all of these purposes and yet permit the electrode to be easily and conveniently changed or adjusted from the open end of the torch.